In 1962, R. B. Merrifield first reported a method for solid phase peptide synthesis (SPPS). One of the major advantages of this technique was the ability to automate the organic synthesis of peptides. However, a commercially viable automated SPPS instrument must efficiently accomplish solvent and reagent delivery, measurement and mixing with resin at the lowest possible cost. Unfortunately, the SPPS instruments produced to date suffer from a number of deficiencies and undesirable or costly compromises.
It is advantageous to be able to run direct, uninterrupted lines from the solvent and reagent supplies. This prevents common flow paths (a potential source of cross-contamination) and the need for intervening valves (which add substantial cost). However, in order to run .uninterrupted lines, the receiving vessel must be open to atmospheric pressure which places severe restrictions on the mixing operation and subsequent solvent flow.
One commercial instrument (Beckman Model 990) does provide uninterrupted lines that discharge into an open measuring vessel. Solvent is gravity fed therefrom into a conical reaction vessel. Since the reaction vessel cannot be tipped, mixing is accomplished by a mechanical stirring rod. This method provides mixing inferior to rocking or inverting mixing, suffers from resin getting stuck up on the sides of the reaction vessel, and introduces mechanical shear forces which may deleteriously impact nascent peptides, especially longer synthetic peptides.
The present invention provides an apparatus and method that creatively solves the prior art deficiencies, while allowing this single instrument to efficiently accommodate a wide variety of synthetic chemistries.